1. Field of the Invention
The present invention relates a scintillator for a gamma ray camera, particularly one in which the crystals form a photo-diffuser for the light generated by scintillation.
2. Description of the Prior Art
Photomultiplier tube structure associated with gamma ray cameras is typically situated far apart from the scintillation light source crystals in order to receive a minimum amount of extraneous light, in order to reduce noise inputs associated with photoelectrons generated at positions with respect to which an individual photomultiplier tube structure is not in alignment. Namely, a large weighting functin Kj causes statistical fluctuations in the generation of the photoelectrons to be excessively emphasized, thereby deteriorating the resolution of the camera.
In an ideal case, it is preferred that gamma ray cameras have a construction such that respective photomultiplier tube structures are be aligned with points of generation of scintillation light from the surface of the gamma ray scintillator camera. Looking at FIG. 1 of the drawings of the present application, for example, there is shown a light source crystal 3 with a scintillation point P generating light upon the incidence of gamma rays, a window 2 and a optical guide 1. Ideally, respective photomultipliers PM.sub.i-3 - P.sub.n.sbsb. +1, where i is an integer, are disposed to receive, exclusively, the respective light rays emitted from the surface of the optical guide 1, originating at the point P in the scintillating crystal 3. For an ideal light spread function Fj(x) the light which is incident upon an individual photomultiplier, such as photomultiplier PM.sub.i-2 does not spread to be incident upon adjacent photomultplier structure. In reality, however, there is a considerable amount of spread of the light generated and various techniques have been proposed to improve the resolution reduced due to light spread.
One technique is the employment of a threshold-amplifier device which limits the signal obtained from a photomultiplier spaced apart from an adjacent photomultiplier, so as to remove signals derived from fluctuations in the generation of photoelectrons. Another technique employs a delay line which reduces the weighting function multiplied by signals generated from a photomultiplier with statistically fluctuating photoelectrons to zero.